Absolutely, it's gotta be a copy of an earlier KSA-100. Signs of some very interesting activity out there.Pity it's a MK1 version.. seems very well designed.
Besides for the ideas already mentioned, here are a few suggestions I thought of:
1) Provision for both TO220, TO92 and the package used for the IRFD MOSFET's.
2) On-board resistors for RC filtering for the input and/or driver stage, since there are on-board supply decoupling capacitors.
3) Capacitors in parallel with the 1N914 diodes as in the KSA50.
4) Legend on the silkscreen indicating which way to turn the bias trimpot for bias increase/decrease (little nice-to-have but can save lots of anguish for those with a heavy screwdriver hand ;-) )
5) Is a separatable driver stage really necessary? I've achieved perfectly stable results without mounting the driver stage on the main heatsink, and it will reduce board size and complexity.
6) Power LED's - besides indicating the obvious, it will also quickly show if the bias is far too high or a heavy current fault or short.
7) 2.4mm board thickness, 70um copper thickness, board colour? (matt yellow/matt green/gloss red/gloss blue/gloss black). I am personally quite fond of the last two..
8) Gold plated over nickel traces (1um)?
9) I suppose I shouldn't even mention the possibility of SMD components.. although a proper COG or NPO ceramic for the 62pF's may work better than silver mica/polystyrene with a much easier layout and shorter signal path. SMD 150R resistors for the LTP pairs will also make them much more compact and efficient, and will make it easier to place the LTP transistors back-to-back for thermal coupling. 1206 form factor is really not that hard to solder. One admitted drawback is that you often end up having the whole board's low-power components in SMD
One of the drawbacks if you work with 0603 SMD stuff all the time.
But that's all now unless people believe in the sound of resistor quality in a design with global feedback such as this one..
Keep 'em coming, these are just a few that popped into my head.
Pierre
Besides for the ideas already mentioned, here are a few suggestions I thought of:
1) Provision for both TO220, TO92 and the package used for the IRFD MOSFET's.
2) On-board resistors for RC filtering for the input and/or driver stage, since there are on-board supply decoupling capacitors.
3) Capacitors in parallel with the 1N914 diodes as in the KSA50.
4) Legend on the silkscreen indicating which way to turn the bias trimpot for bias increase/decrease (little nice-to-have but can save lots of anguish for those with a heavy screwdriver hand ;-) )
5) Is a separatable driver stage really necessary? I've achieved perfectly stable results without mounting the driver stage on the main heatsink, and it will reduce board size and complexity.
6) Power LED's - besides indicating the obvious, it will also quickly show if the bias is far too high or a heavy current fault or short.
7) 2.4mm board thickness, 70um copper thickness, board colour? (matt yellow/matt green/gloss red/gloss blue/gloss black). I am personally quite fond of the last two..
8) Gold plated over nickel traces (1um)?
9) I suppose I shouldn't even mention the possibility of SMD components.. although a proper COG or NPO ceramic for the 62pF's may work better than silver mica/polystyrene with a much easier layout and shorter signal path. SMD 150R resistors for the LTP pairs will also make them much more compact and efficient, and will make it easier to place the LTP transistors back-to-back for thermal coupling. 1206 form factor is really not that hard to solder. One admitted drawback is that you often end up having the whole board's low-power components in SMD
One of the drawbacks if you work with 0603 SMD stuff all the time.But that's all now unless people believe in the sound of resistor quality in a design with global feedback such as this one..
Keep 'em coming, these are just a few that popped into my head.
Pierre
Sounds ok for me
Pierre,
one question: whats your reason for choosing the 2.4 mm board thickness? isnt the 1.6 mm
an all-rounder (cheaper), especially if choosing 70µm Cu?
Just wandering.
The rest of your suggestions looks fine (but I will use the silvered mica 62pF because I already have them) .
But I was also thinking of this:
My chassis will be 150 mm heigh (internal), Is it possible to have the board not wider than, say 140-148mm (but it could be longer). If not, it will not fit standing in my chassis and that will make a fit-problem for my project.
Regards
Pierre,
one question: whats your reason for choosing the 2.4 mm board thickness? isnt the 1.6 mm
an all-rounder (cheaper), especially if choosing 70µm Cu?
Just wandering.
The rest of your suggestions looks fine (but I will use the silvered mica 62pF because I already have them) .
But I was also thinking of this:
My chassis will be 150 mm heigh (internal), Is it possible to have the board not wider than, say 140-148mm (but it could be longer). If not, it will not fit standing in my chassis and that will make a fit-problem for my project.
Regards
Flodstroem,
The width you mention is unlikely to be exceeded, in fact I think it will be more or less the same size as the PinkMouse KSA50 boards. Especially if the SMD resistors are used, the board can become very compact and even possibly be smaller than the KSA50 ones. Of course it depends on the application, those using fan-blocks as in the original would like a short, yet not so wide limitation
I suggested 2.4mm since in my experience people, especially amateurs, tend to treat their boards rather roughly and a thicker board will be harder to bend or break. The added thickness will not make an electrical difference at the low frequencies used. I don't know about overseas production houses, but the local ones I deal with charge little or no extra for thicker boards.
Don't look for exotic caps for the 62pF, but rather linearity and to a certain degree heat tolerance. Some super-exotic caps may be appealling, but their physical size counts against them. I personally prefer polystrene since they're generally smaller than mica and fits in underneath the TO220 casing instead of next to it. An SMD ceramic will of course be right next to the device leads but I'm sure not many people will use it.
The width you mention is unlikely to be exceeded, in fact I think it will be more or less the same size as the PinkMouse KSA50 boards. Especially if the SMD resistors are used, the board can become very compact and even possibly be smaller than the KSA50 ones. Of course it depends on the application, those using fan-blocks as in the original would like a short, yet not so wide limitation
I suggested 2.4mm since in my experience people, especially amateurs, tend to treat their boards rather roughly and a thicker board will be harder to bend or break. The added thickness will not make an electrical difference at the low frequencies used. I don't know about overseas production houses, but the local ones I deal with charge little or no extra for thicker boards.
Don't look for exotic caps for the 62pF, but rather linearity and to a certain degree heat tolerance. Some super-exotic caps may be appealling, but their physical size counts against them. I personally prefer polystrene since they're generally smaller than mica and fits in underneath the TO220 casing instead of next to it. An SMD ceramic will of course be right next to the device leads but I'm sure not many people will use it.
1) Provision for both TO220, TO92 and the package used for the IRFD MOSFET's.
> TO-220? Thats going to take up some real estate on the board! TO-220 is pretty much an obsolete package in the US. I agree with the other two though
On-board resistors for RC filtering for the input and/or driver stage, since there are on-board supply decoupling capacitors.
>Better yet lets take this one step further and include the extra power supply board to make this a KMA-100 project.
3) Capacitors in parallel with the 1N914 diodes as in the KSA50.
>K
4) Legend on the silkscreen indicating which way to turn the bias trimpot for bias increase/decrease (little nice-to-have but can save lots of anguish for those with a heavy screwdriver hand ;-) )
>K
5) Is a separatable driver stage really necessary? I've achieved perfectly stable results without mounting the driver stage on the main heatsink, and it will reduce board size and complexity.
> Stable results can be had but longer driver life will be had by properly heatsinking them. Even Krell's drivers ran way too hot because of too little sinking! On Pinky's version you didn't have to snap off the driver board if you didn't want to. I say make this part the same and you can leave it on or take it off.
6) Power LED's - besides indicating the obvious, it will also quickly show if the bias is far too high or a heavy current fault or short.
Come on now....
7) 2.4mm board thickness, 70um copper thickness, board colour? (matt yellow/matt green/gloss red/gloss blue/gloss black). I am personally quite fond of the last two..
>If everyone wants to pay for that. While I'm willing to front the $$ and have the boards done again we would have to be in aggreance on the pricing. There is a big price difference. I had the fist batch of Pinky's boards done in 2.4mm and the second batch done thinner with a considerable cost savings. Since I still sit on lots of those boards I vote to keep board cost down. Of course if someone else wants to front the $$ thats fine too.
8) Gold plated over nickel traces (1um)?
>Yes, the cost is minimal.
9) I suppose I shouldn't even mention the possibility of SMD components.. although a proper COG or NPO ceramic for the 62pF's may work better than silver mica/polystyrene with a much easier layout and shorter signal path. SMD 150R resistors for the LTP pairs will also make them much more compact and efficient, and will make it easier to place the LTP transistors back-to-back for thermal coupling. 1206 form factor is really not that hard to solder. One admitted drawback is that you often end up having the whole board's low-power components in SMD One of the drawbacks if you work with 0603 SMD stuff all the time.
But that's all now unless people believe in the sound of resistor quality in a design with global feedback such as this one..
Definatley no SMD. Very few can work with it properly and the parts cost is very high. As youmentioned above the whole amp will run quite warm and reach its own thermal equilebrim. Even the solder for SMDis rediclously expensive. Yes the brand of resistor does have a bearing on sound character even in this amp. I can speak with experience here since I've built 5 KSA-50's three of them utilizing different resistors. Vishays still provide the best character IMHO.
Are we designing a new amp or kloning the KSA-100 MK-2/ KMA-100? If the end result here is not at least close like the KSA-50 was then I'll just go ahead and go back to the Tektronix terminal strip method I was going to do. P to P has its merits too... especially when using silver contact points on ceramic strips!
Mark
> TO-220? Thats going to take up some real estate on the board! TO-220 is pretty much an obsolete package in the US. I agree with the other two though
On-board resistors for RC filtering for the input and/or driver stage, since there are on-board supply decoupling capacitors.
>Better yet lets take this one step further and include the extra power supply board to make this a KMA-100 project.
3) Capacitors in parallel with the 1N914 diodes as in the KSA50.
>K
4) Legend on the silkscreen indicating which way to turn the bias trimpot for bias increase/decrease (little nice-to-have but can save lots of anguish for those with a heavy screwdriver hand ;-) )
>K
5) Is a separatable driver stage really necessary? I've achieved perfectly stable results without mounting the driver stage on the main heatsink, and it will reduce board size and complexity.
> Stable results can be had but longer driver life will be had by properly heatsinking them. Even Krell's drivers ran way too hot because of too little sinking! On Pinky's version you didn't have to snap off the driver board if you didn't want to. I say make this part the same and you can leave it on or take it off.
6) Power LED's - besides indicating the obvious, it will also quickly show if the bias is far too high or a heavy current fault or short.
Come on now....
7) 2.4mm board thickness, 70um copper thickness, board colour? (matt yellow/matt green/gloss red/gloss blue/gloss black). I am personally quite fond of the last two..
>If everyone wants to pay for that. While I'm willing to front the $$ and have the boards done again we would have to be in aggreance on the pricing. There is a big price difference. I had the fist batch of Pinky's boards done in 2.4mm and the second batch done thinner with a considerable cost savings. Since I still sit on lots of those boards I vote to keep board cost down. Of course if someone else wants to front the $$ thats fine too.
8) Gold plated over nickel traces (1um)?
>Yes, the cost is minimal.
9) I suppose I shouldn't even mention the possibility of SMD components.. although a proper COG or NPO ceramic for the 62pF's may work better than silver mica/polystyrene with a much easier layout and shorter signal path. SMD 150R resistors for the LTP pairs will also make them much more compact and efficient, and will make it easier to place the LTP transistors back-to-back for thermal coupling. 1206 form factor is really not that hard to solder. One admitted drawback is that you often end up having the whole board's low-power components in SMD One of the drawbacks if you work with 0603 SMD stuff all the time.
But that's all now unless people believe in the sound of resistor quality in a design with global feedback such as this one..
Definatley no SMD. Very few can work with it properly and the parts cost is very high. As youmentioned above the whole amp will run quite warm and reach its own thermal equilebrim. Even the solder for SMDis rediclously expensive. Yes the brand of resistor does have a bearing on sound character even in this amp. I can speak with experience here since I've built 5 KSA-50's three of them utilizing different resistors. Vishays still provide the best character IMHO.
Are we designing a new amp or kloning the KSA-100 MK-2/ KMA-100? If the end result here is not at least close like the KSA-50 was then I'll just go ahead and go back to the Tektronix terminal strip method I was going to do. P to P has its merits too... especially when using silver contact points on ceramic strips!
Mark
Regarding a separatable driver board ?
What components do you mean will be located at this board area, the Q14-16/R39-41 only, or?
Regarding the schematics:
Could the double pair of MJ15030/31 drive 6 pair of MJ15003/4 or should I implement a third driver pair to drive the extra two MJ15003/4 pair? My reason for that is to rise the SOA and also for to drive even lower impedance speakers. If puting in a third driver pair, could I use the same value (75R0) as the originals or should I change the emitter resistors value (to a higher value ?)
Mark:
Is it a drawback or a benefit to locate the driver stage on same heat sink (and board) where the power stage/transistors are mounted (if not taking any practical issue in to account)?
Any wise answer will be appreciated.
Regards
What components do you mean will be located at this board area, the Q14-16/R39-41 only, or?
Regarding the schematics:
Could the double pair of MJ15030/31 drive 6 pair of MJ15003/4 or should I implement a third driver pair to drive the extra two MJ15003/4 pair? My reason for that is to rise the SOA and also for to drive even lower impedance speakers. If puting in a third driver pair, could I use the same value (75R0) as the originals or should I change the emitter resistors value (to a higher value ?)
Mark:
Is it a drawback or a benefit to locate the driver stage on same heat sink (and board) where the power stage/transistors are mounted (if not taking any practical issue in to account)?
Any wise answer will be appreciated.
Regards
drivers and outputs...
An observation, both personal and reported elsewhere (Doug Self has good charts in his book)...
For any given level of output current, more output transistors sharing the load puts less of a load on the drivers. Basically the lower current in each transistor puts it at better point on the hfe curve, so the drivers have to supply less current. Thus if you add outputs, you pretty much don't need to add drivers. If you want three or four pairs of 15003/4's per driver pair, just make sure you use the right size emitter resistors and you are good to go...
IMHO more drivers are not necessary and will needlessly complicate the board, plus I hate having areas of boards not populated, makes things look unfinished.
Bearing in mind that 4 x MJ2119x pairs can already do >50A peaks, requiring a lot more output current (say 100A) always means more outputs, and can mean more drivers. If anyone has a special load they are planning to drive to extremes with these amps (or the KSA50) and wants to talk about how to ensure the output and driver stages can handle it they can post here or email me...
Stuart
An observation, both personal and reported elsewhere (Doug Self has good charts in his book)...
For any given level of output current, more output transistors sharing the load puts less of a load on the drivers. Basically the lower current in each transistor puts it at better point on the hfe curve, so the drivers have to supply less current. Thus if you add outputs, you pretty much don't need to add drivers. If you want three or four pairs of 15003/4's per driver pair, just make sure you use the right size emitter resistors and you are good to go...
IMHO more drivers are not necessary and will needlessly complicate the board, plus I hate having areas of boards not populated, makes things look unfinished.
Bearing in mind that 4 x MJ2119x pairs can already do >50A peaks, requiring a lot more output current (say 100A) always means more outputs, and can mean more drivers. If anyone has a special load they are planning to drive to extremes with these amps (or the KSA50) and wants to talk about how to ensure the output and driver stages can handle it they can post here or email me...
Stuart
Stuart Easson,
Yes I agree to that.
Do you have any experience to this issue:
Is it a drawback or a benefit to locate the driver stage on same heat sink/power board where the power stage/transistors are mounted (if not taking any practical issue in to account)?
This location of driver stage will solve the issue regarding heat sinking of the driver transistors (no need for a special heat sink on the input/driver board).
Thanks for your advice.
Regards
Yes I agree to that.
Do you have any experience to this issue:
Is it a drawback or a benefit to locate the driver stage on same heat sink/power board where the power stage/transistors are mounted (if not taking any practical issue in to account)?
This location of driver stage will solve the issue regarding heat sinking of the driver transistors (no need for a special heat sink on the input/driver board).
Thanks for your advice.
Regards
driver heatsinks
I have built the amp both ways, and can't say that either solution struck me as technically better than the other, though less 'flying' leads seems neater to me. Having the driver heatsink away from other components might be good from the perspective of not cooking them...
For lower output levels, ~70W class A, I had the drivers on a different heatsink from the outputs. I arbitrarily decided I wanted them cooler than the relatively hot outputs, and sized the driver heatsink accordingly. For the bigger amp, I mounted the drivers on the same heatsink as the outputs, which had fan cooling. I used point to point wiring for the driver and output emitter resistors...
HTH
Stuart
I have built the amp both ways, and can't say that either solution struck me as technically better than the other, though less 'flying' leads seems neater to me. Having the driver heatsink away from other components might be good from the perspective of not cooking them...
For lower output levels, ~70W class A, I had the drivers on a different heatsink from the outputs. I arbitrarily decided I wanted them cooler than the relatively hot outputs, and sized the driver heatsink accordingly. For the bigger amp, I mounted the drivers on the same heatsink as the outputs, which had fan cooling. I used point to point wiring for the driver and output emitter resistors...
HTH
Stuart
I'm with Stuart on not having alot of flying leads. Mounting them to the main sink or another sink as he did is alot sturdier affair. My present KSA-50 has them mounted to the main sink and thermal tracking is excellent... In fact both channels are mounted on a common extrusion and both channels operate in a very stable mode. I think that as long as the bias device is mounted to the same sink as the drivers it's all also going to track very well. The output stage has that as it's refrence so to say. With a seperate board its just allot easier and allot more sturdy to mount them... or leave the board in one piece of you like.....
The whimpy heat sinks Krell used on the drivers was not enough area... Those devices ran so hot you couldn't touch them.... not a good thing to have with a plastic device.
P.Watts,
I've never had troubles with any G-10 board breaking. Whats more important than thicker material are getting 2 oz traces. They hold up better to a soldering iron's heat than 1 oz. or thinner. Clearly lets point out what board aspects are the more important here... thickness is ner an issue till we get into the flex board thickness..... even those are quite sturdy! Again, this needs to be a close Klone of the amp... not a re-design.
Mark
The whimpy heat sinks Krell used on the drivers was not enough area... Those devices ran so hot you couldn't touch them.... not a good thing to have with a plastic device.
P.Watts,
I've never had troubles with any G-10 board breaking. Whats more important than thicker material are getting 2 oz traces. They hold up better to a soldering iron's heat than 1 oz. or thinner. Clearly lets point out what board aspects are the more important here... thickness is ner an issue till we get into the flex board thickness..... even those are quite sturdy! Again, this needs to be a close Klone of the amp... not a re-design.
Mark
VP/VN FETs
Regarding those V-DMOS-FETs VP/VN0210N5 (Q5-Q8) Mark suggested:
Yes I think they can do the job, but an even closer match (and safer) could be the ZVN/P2110G (Zetex, dont know if Mark have had a look at them). These have nearly same spec as the older originals, but a slightly higher RDS on( Gate threshold 0.8-3.5V, I drain 3-6Amps, Gate charge 60-100pF and RDS-on 4-8 ohms, max.power diss. 2Watts). Only drawback is the package: SOT223!!?? But they could easily be soldered (as SMD) on back of PCB because they are physically bigger than the 1206 or SOT 23 package. But I dont know if this is an issue?
Regards
Regarding those V-DMOS-FETs VP/VN0210N5 (Q5-Q8) Mark suggested:
Yes I think they can do the job, but an even closer match (and safer) could be the ZVN/P2110G (Zetex, dont know if Mark have had a look at them). These have nearly same spec as the older originals, but a slightly higher RDS on( Gate threshold 0.8-3.5V, I drain 3-6Amps, Gate charge 60-100pF and RDS-on 4-8 ohms, max.power diss. 2Watts). Only drawback is the package: SOT223!!?? But they could easily be soldered (as SMD) on back of PCB because they are physically bigger than the 1206 or SOT 23 package. But I dont know if this is an issue?
Regards
Interesting comments. Point taken about the board thickness, didn't know the price difference was so large overseas - here it's benign (If I remember the Delta Audio boards were also 2.4mm). Didn't know it's such a sensitive issue. Thinner it will be then.. although if I only do the Gerbers, the matter of finish, thickness etc. is out of my hands anyway
I'm a bit puzzled with if we are designing a new amp - so far there's been a lot of changes made to both the KSA50 and KSA100 designs, some by choice, some by lack of component availability. Parameters such as board thickness is hardly a deviation from the original; some of the other mods that are generally accepted ARE however. Swopping between various transistors esp in the output stage will have a more profound influence on the end result than resistor type/brand. Where do you draw the line between "improvised original" and "new"? It becomes a philosophical dilemma; Doug Self would have a field day with this topic. Krell themselves made huge changes to the KSA100Mk2 vs the Mk1; yet both remain very popular. A few comparably minor changes here and there is unlikely to ruin the character. In fact, there's a common concencus among many Krell owners that as the complexity of the KSA designs (e.g. sliding bias) increased over the years, the quality didn't follow, and I know of somebody whose KSA200 is standing in a corner in favour of a much older KSA100 Mk2. There's a reason why the KSA50, with its very old design, is a hall of famer... Just shows that bells and whistles doesn't necessarily improve quality.
@Mark - I don't know what you're referring to to SMD being expensive. SMD parts are much cheaper than leaded ones, it works out on less than $0.50 for 100 resistors. Normal metal film will typically be at least twice that price, and Dales $20. And it can be soldered with plain normal solder, no special stuff needed for that. Solder paste et al isn't necessary for these big things. 1206 can be soldered with a run-off-the mill $10 iron and eyes younger than 60years old, but OK I didn't think the idea will catch on anyway.
The SOT-23 packages will work excellent and the Zetex FET's mentioned by Flodstroem appears to be good substitutions (esp since they won't need any heatsinking), but we'll have to see if people are OK with the package. I still encourage the use of the IRFD types, they've a small, yet manageable package with good specs and fairly low cost. Fortunately it's easy to provide support for both them and TO92, but SOT23 as well will start pushing it.
I agree with Andrew - what IS the US using if not TO-220? Besides the newer D-PAK and similar type casings, but given the anti-SMD sentiment that's out as well. To my knowledge there's no medium-power leaded substitute for TO-220, but it's admitted an overly large package for this particular application.
Concerning a different power supply board for the input and driver stage - if there're separate supply connections people can connect whatever they want from an external source. Some would like a regulated one, others just a separated one. Plus it will take up too much extra board space. Adding pads for resistors take up little space and can just be bridged with a link by those not wanting to use them.
A separate supply will of course be a good idea, especially if the main supply's a bit lacking. However, any change from the simple resistor-zener combo is likely to result in turn-on thump, so unless the protection circuitry is used it may be an issue for some.
Even with a fairly small driver heatsink I got lower heatsink temperatures than the main heatsink's. True, that blue driver sink on the original KSA100 is too small and runs damn hot, BUT those blocks run even hotter - there's still part of my skin left on one that I serviced last year (and no the bias wasn't too high or any other anomaly). If you need the drivers to run cooler on the main sink than on a mid-sized separate heatsink, the main sink should be a substantial one. But OK, with a snappable board builders can decide for themself according to their situation.
I'm a bit puzzled with if we are designing a new amp - so far there's been a lot of changes made to both the KSA50 and KSA100 designs, some by choice, some by lack of component availability. Parameters such as board thickness is hardly a deviation from the original; some of the other mods that are generally accepted ARE however. Swopping between various transistors esp in the output stage will have a more profound influence on the end result than resistor type/brand. Where do you draw the line between "improvised original" and "new"? It becomes a philosophical dilemma; Doug Self would have a field day with this topic. Krell themselves made huge changes to the KSA100Mk2 vs the Mk1; yet both remain very popular. A few comparably minor changes here and there is unlikely to ruin the character. In fact, there's a common concencus among many Krell owners that as the complexity of the KSA designs (e.g. sliding bias) increased over the years, the quality didn't follow, and I know of somebody whose KSA200 is standing in a corner in favour of a much older KSA100 Mk2. There's a reason why the KSA50, with its very old design, is a hall of famer... Just shows that bells and whistles doesn't necessarily improve quality.
@Mark - I don't know what you're referring to to SMD being expensive. SMD parts are much cheaper than leaded ones, it works out on less than $0.50 for 100 resistors. Normal metal film will typically be at least twice that price, and Dales $20. And it can be soldered with plain normal solder, no special stuff needed for that. Solder paste et al isn't necessary for these big things. 1206 can be soldered with a run-off-the mill $10 iron and eyes younger than 60years old, but OK I didn't think the idea will catch on anyway.
The SOT-23 packages will work excellent and the Zetex FET's mentioned by Flodstroem appears to be good substitutions (esp since they won't need any heatsinking), but we'll have to see if people are OK with the package. I still encourage the use of the IRFD types, they've a small, yet manageable package with good specs and fairly low cost. Fortunately it's easy to provide support for both them and TO92, but SOT23 as well will start pushing it.
I agree with Andrew - what IS the US using if not TO-220?
Besides the newer D-PAK and similar type casings, but given the anti-SMD sentiment that's out as well. To my knowledge there's no medium-power leaded substitute for TO-220, but it's admitted an overly large package for this particular application.Concerning a different power supply board for the input and driver stage - if there're separate supply connections people can connect whatever they want from an external source. Some would like a regulated one, others just a separated one. Plus it will take up too much extra board space. Adding pads for resistors take up little space and can just be bridged with a link by those not wanting to use them.
A separate supply will of course be a good idea, especially if the main supply's a bit lacking. However, any change from the simple resistor-zener combo is likely to result in turn-on thump, so unless the protection circuitry is used it may be an issue for some.
Even with a fairly small driver heatsink I got lower heatsink temperatures than the main heatsink's. True, that blue driver sink on the original KSA100 is too small and runs damn hot, BUT those blocks run even hotter - there's still part of my skin left on one that I serviced last year (and no the bias wasn't too high or any other anomaly). If you need the drivers to run cooler on the main sink than on a mid-sized separate heatsink, the main sink should be a substantial one. But OK, with a snappable board builders can decide for themself according to their situation.
PWatts,
I wrote SOT-223 for the Zetex FETs, not SOT-23 A SOT-223 package is considerable bigger than the small SOT-23 Just for your knowledge (but you already know that).
Does somebody know the price for those Zetex FETs (ZVN/ZVP2110G)? If placing those transistors in a straight line on the board you could easily mount a small AL-plate or strip over the transistors for to get same temp. (as in the originals Krell).
Hope your design-work could start soon, I want to build KSA 100mkII clones...................
Regards
I wrote SOT-223 for the Zetex FETs, not SOT-23 A SOT-223 package is considerable bigger than the small SOT-23 Just for your knowledge (but you already know that).
Does somebody know the price for those Zetex FETs (ZVN/ZVP2110G)? If placing those transistors in a straight line on the board you could easily mount a small AL-plate or strip over the transistors for to get same temp. (as in the originals Krell).
Hope your design-work could start soon, I want to build KSA 100mkII clones...................
Regards
Whoops sorry, I misread that extra '2' in 223
Well I think most of the details has been sorted out, so as soon as we have concensus over the FET packages I'll start with the layout. In fact, I'l start tonight and just dodge that particular area for now. Fortunately on a 2-sided board it's easy to chage pin layouts later on. Just need to go make some new footprints for a few components but that'll take quick.
If there're no serious objections/moaning about the layout or something terrible doesn't happen to stall my time, I cannot see why it won't be finished in 10days or so. The combination between Al's board and the original KSA100 for guidance will make it quite easy to finish, plus it's not nearly as complex as the ones I deal with daily.
Well I think most of the details has been sorted out, so as soon as we have concensus over the FET packages I'll start with the layout. In fact, I'l start tonight and just dodge that particular area for now. Fortunately on a 2-sided board it's easy to chage pin layouts later on. Just need to go make some new footprints for a few components but that'll take quick.
If there're no serious objections/moaning about the layout or something terrible doesn't happen to stall my time, I cannot see why it won't be finished in 10days or so. The combination between Al's board and the original KSA100 for guidance will make it quite easy to finish, plus it's not nearly as complex as the ones I deal with daily.
Very true.. unfortuately Krell owners are very picky about any modifications, particularly cosmetic, made to their babies. Took me months to convince a guy to let me replace his dried out Roederstein feedback electrolytics with proper Black Gate NX's.. and now he sings the praises of the improvement fortunately.
PWatts,
What type of input/differential stage transistors have you decided to use, MPSAxx or the original 2SC/2SA ? If somebody want to use the original transistors, remember those do not have the same leg configuration as MPSAxx (is it possible to have a foot-print that suits both configurations?????).
Just some thoughts
Regards
What type of input/differential stage transistors have you decided to use, MPSAxx or the original 2SC/2SA ? If somebody want to use the original transistors, remember those do not have the same leg configuration as MPSAxx (is it possible to have a foot-print that suits both configurations?????).
Just some thoughts
Regards
I think the best choice is the BC546/556 types - they're fast, cheap, easily available and provided the best simulated results. So far I've gathered most people have used MPS/BC/2N transistors anyway. The MPS ones are easy to use; just reverse their orientation. But, once again the voice of the masses should be the deciding factor.
Unless people speak up, the design criteria will therefore be the same as with Al's KSA50, with just the added components. The jury's still out on the SOT223 packages, so until there's clarity on that topic I'll just route around it.
Maybe we should just take a poll as to how many people would like to participate in a group buy to determine if it's viable. Mark, you've been through the motions, would you please manage that area? I think since the board will be roughly the same as Al's, the pricing will be closely similar, depending on price breaks for the order quantities.
Another question: Should we go for the original 4 pairs output transistors, or increase it to 6 pairs i.e. twice the KSA50 klone?
Unless people speak up, the design criteria will therefore be the same as with Al's KSA50, with just the added components. The jury's still out on the SOT223 packages, so until there's clarity on that topic I'll just route around it.
Maybe we should just take a poll as to how many people would like to participate in a group buy to determine if it's viable. Mark, you've been through the motions, would you please manage that area? I think since the board will be roughly the same as Al's, the pricing will be closely similar, depending on price breaks for the order quantities.
Another question: Should we go for the original 4 pairs output transistors, or increase it to 6 pairs i.e. twice the KSA50 klone?
Im going to use 6 pair
mostly because I have planned to do it, I have all the parts (power transistors: MJ15003/4) at home. But regardless of my plans, six pairs could be beneficial for those who wants to use their stock-part power transistors that does not have the same rugged SOA (plastic TO-3P) as the original, TO-3 metal transistors, and by adding two pair extra they will reach same level of SOA, (or am I wrong about this?)
Regards
mostly because I have planned to do it, I have all the parts (power transistors: MJ15003/4) at home. But regardless of my plans, six pairs could be beneficial for those who wants to use their stock-part power transistors that does not have the same rugged SOA (plastic TO-3P) as the original, TO-3 metal transistors, and by adding two pair extra they will reach same level of SOA, (or am I wrong about this?)
Regards